DON'T BE DECLINED

You CAN be denied a mortgage loan AFTER you have been preapproved

many factors can derail the mortgage process - you need to be careful with your finances between your pre approval, approval and closing date

1. avoid making big purchases on your credit card(s) or taking out other loans ie. buying a new vehicle - this can shift the LTV (loan to value) ratio and your credit score which can alter what the bank will lend you

Tips 
keep your finances as is (unless you are bettering your situation ie paying off credit, saving more)
don't tap in to your savings aside from your deposit/downpayment
don't switch jobs
don't do anything that can reduce your assets or increase your debt